Progress with macros

A short recap:
* Macro expansion now works finely for instance macro invocations
* Macros are now hidden behind -Xmacros
* Bodies of macros now have "import _context._" in their preamble
* Macros are now loaded from classpath, much like regular libraries
* Macros can now override methods (in that case macro expansion
  does not crash if macro is not found, it just falls back to super)

Review by @odersky.

2 files changed, 188 insertions, 0 deletions

diff --git a/test/files/run/macro-range/macro_range_1.scala b/test/files/run/macro-range/macro_range_1.scala
new file mode 100644
index 0000000000..15a018fcff
--- /dev/null
+++ b/test/files/run/macro-range/macro_range_1.scala
@@ -0,0 +1,94 @@
+import reflect.api.Modifier
+import reflect.macro.Context
+
+abstract class RangeDefault {
+  val from, to: Int
+  def foreach(f: Int => Unit) = {
+    var i = from
+    while (i < to) { f(i); i += 1 }
+  }
+}
+
+/** This class should go into reflect.macro once it is a bit more stable. */
+abstract class Utils {
+  val context: Context
+  import context._
+
+  class TreeSubstituter(from: List[Symbol], to: List[Tree]) extends Transformer {
+    override def transform(tree: Tree): Tree = tree match {
+      case Ident(_) =>
+        def subst(from: List[Symbol], to: List[Tree]): Tree =
+          if (from.isEmpty) tree
+          else if (tree.symbol == from.head) to.head.duplicate // TODO: does it ever make sense *not* to perform a shallowDuplicate on `to.head`?
+          else subst(from.tail, to.tail);
+        subst(from, to)
+      case _ =>
+        val tree1 = super.transform(tree)
+        if (tree1 ne tree) tree1.tpe = null
+        tree1
+    }
+  }
+  def makeApply(fn: Tree, args: List[Tree]): Tree = fn match {
+    case Function(vparams, body) => 
+      new TreeSubstituter(vparams map (_.symbol), args) transform body
+    case Block(stats, expr) =>
+      Block(stats, makeApply(expr, args))
+    case _ => 
+      println("no beta on "+fn+" "+fn.getClass)
+      Apply(fn, args)
+  }
+  def makeWhile(lname: TermName, cond: Tree, body: Tree): Tree = {
+    val continu = Apply(Ident(lname), Nil)
+    val rhs = If(cond, Block(List(body), continu), Literal(Constant()))
+    LabelDef(lname, Nil, rhs)
+  }
+  def makeBinop(left: Tree, op: String, right: Tree): Tree =
+    Apply(Select(left, newTermName(op)), List(right))
+}
+
+class Range(val from: Int, val to: Int) extends RangeDefault {
+  override def macro foreach(f: Int => Unit): Unit = {
+    println("macro-expand, _this = "+ _this) 
+    import _context._
+    object utils extends Utils {
+      val context: _context.type = _context
+    }
+    import utils._
+
+    val initName = newTermName("<init>")
+    // Either:
+    //   scala"{ var i = $low; val h = $hi; while (i < h) { $f(i); i = i + 1 } }
+    // or:
+    //   scala"($_this: RangeDefault).foreach($f)"
+    _this match {
+      case Apply(Select(New(tpt), initName), List(lo, hi)) if tpt.symbol.fullName == "Range" =>
+        val iname = newTermName("$i")
+        val hname = newTermName("$h")
+        def iref = Ident(iname)
+        def href = Ident(hname)
+        val labelname = newTermName("$while")
+        val cond = makeBinop(iref, "$less", href)
+        val body = Block(
+            List(makeApply(f, List(iref))),
+            Assign(iref, makeBinop(iref, "$plus", Literal(Constant(1)))))
+        tools.nsc.util.trace("generated: ")(
+        Block(
+          List(
+            ValDef(Modifiers(Set(Modifier.mutable)), iname, TypeTree(), lo),
+            ValDef(Modifiers(), hname, TypeTree(), hi)),
+          makeWhile(labelname, cond, body)))
+      case _ =>
+        Apply(
+          Select(
+            Typed(_this, Ident(newTypeName("RangeDefault"))),
+            newTermName("foreach")),
+          List(f))
+    }
+  }
+}
+
+object Test extends App {
+
+  new Range(1, 10) foreach println
+
+}
diff --git a/test/files/run/macro-range/macro_range_2.scala b/test/files/run/macro-range/macro_range_2.scala
new file mode 100644
index 0000000000..15a018fcff
--- /dev/null
+++ b/test/files/run/macro-range/macro_range_2.scala
@@ -0,0 +1,94 @@
+import reflect.api.Modifier
+import reflect.macro.Context
+
+abstract class RangeDefault {
+  val from, to: Int
+  def foreach(f: Int => Unit) = {
+    var i = from
+    while (i < to) { f(i); i += 1 }
+  }
+}
+
+/** This class should go into reflect.macro once it is a bit more stable. */
+abstract class Utils {
+  val context: Context
+  import context._
+
+  class TreeSubstituter(from: List[Symbol], to: List[Tree]) extends Transformer {
+    override def transform(tree: Tree): Tree = tree match {
+      case Ident(_) =>
+        def subst(from: List[Symbol], to: List[Tree]): Tree =
+          if (from.isEmpty) tree
+          else if (tree.symbol == from.head) to.head.duplicate // TODO: does it ever make sense *not* to perform a shallowDuplicate on `to.head`?
+          else subst(from.tail, to.tail);
+        subst(from, to)
+      case _ =>
+        val tree1 = super.transform(tree)
+        if (tree1 ne tree) tree1.tpe = null
+        tree1
+    }
+  }
+  def makeApply(fn: Tree, args: List[Tree]): Tree = fn match {
+    case Function(vparams, body) => 
+      new TreeSubstituter(vparams map (_.symbol), args) transform body
+    case Block(stats, expr) =>
+      Block(stats, makeApply(expr, args))
+    case _ => 
+      println("no beta on "+fn+" "+fn.getClass)
+      Apply(fn, args)
+  }
+  def makeWhile(lname: TermName, cond: Tree, body: Tree): Tree = {
+    val continu = Apply(Ident(lname), Nil)
+    val rhs = If(cond, Block(List(body), continu), Literal(Constant()))
+    LabelDef(lname, Nil, rhs)
+  }
+  def makeBinop(left: Tree, op: String, right: Tree): Tree =
+    Apply(Select(left, newTermName(op)), List(right))
+}
+
+class Range(val from: Int, val to: Int) extends RangeDefault {
+  override def macro foreach(f: Int => Unit): Unit = {
+    println("macro-expand, _this = "+ _this) 
+    import _context._
+    object utils extends Utils {
+      val context: _context.type = _context
+    }
+    import utils._
+
+    val initName = newTermName("<init>")
+    // Either:
+    //   scala"{ var i = $low; val h = $hi; while (i < h) { $f(i); i = i + 1 } }
+    // or:
+    //   scala"($_this: RangeDefault).foreach($f)"
+    _this match {
+      case Apply(Select(New(tpt), initName), List(lo, hi)) if tpt.symbol.fullName == "Range" =>
+        val iname = newTermName("$i")
+        val hname = newTermName("$h")
+        def iref = Ident(iname)
+        def href = Ident(hname)
+        val labelname = newTermName("$while")
+        val cond = makeBinop(iref, "$less", href)
+        val body = Block(
+            List(makeApply(f, List(iref))),
+            Assign(iref, makeBinop(iref, "$plus", Literal(Constant(1)))))
+        tools.nsc.util.trace("generated: ")(
+        Block(
+          List(
+            ValDef(Modifiers(Set(Modifier.mutable)), iname, TypeTree(), lo),
+            ValDef(Modifiers(), hname, TypeTree(), hi)),
+          makeWhile(labelname, cond, body)))
+      case _ =>
+        Apply(
+          Select(
+            Typed(_this, Ident(newTypeName("RangeDefault"))),
+            newTermName("foreach")),
+          List(f))
+    }
+  }
+}
+
+object Test extends App {
+
+  new Range(1, 10) foreach println
+
+}